Why a woman’s age at time of marriage matters, and what this tells us about the apex fallacy

The basic relationship between a woman’s age at the time of marriage and her likelihood of divorcing is fairly well known. As the chart above (source) shows, women who marry later are less likely to divorce within the first ten years of marriage than those who marry when very young. However, what is seldom discussed is why this is the case. The standard assumption is that women who wait longer are more mature, better able to pick a husband they can remain faithful to, and more ready for marriage. Also, women who attend college generally marry a bit later, and college attendance correlates strongly with IQ, which has a very strong inverse correlation with divorce. Undoubtedly there is some truth to these reasons, but there is something else very important going on. A woman’s likelihood of divorcing in any given year is inversely correlated to her age. Young women in the peak of their sexual marketplace power are far more likely to divorce than older women are. The chart below demonstrates this using data from the United Kingdom’s Office Of National Statistics (view table):

Note how aside from the very youngest age brackets, a woman in the UK’s likelihood of divorcing correlates strongly with her perceived ability to remarry. The UK under 20 and 20-24 age brackets are perplexing, because they defy conventional wisdom on very young marriage, the US data on early marriage divorce rates, as well as expectations based on the sexual marketplace. With this in mind, I suspect that women who marry that young in the UK are bucking the trend enough that they are a much more dedicated group regarding marriage. The last chart was just a snapshot in time, but the basic effect has been remarkably stable in the UK for as far back as data is available:

Leaving aside the volatile under 20 age bracket, the lines almost never cross. The only change is that the 20-24 year old bracket has moved between being the most likely to divorce, the second most likely to divorce, and the third most likely to divorce. But the trend for women starting in their late 20s has always been the same; the older they are, the less likely they are to divorce. This has remained the case even as the age of first marriage has continued to grow. This isn’t simply about divorces occurring in the very beginning of marriage. There is a much stronger pattern involved here.

I have yet to find anyone who splits the US data out this way, but just this week I found the missing component I needed to roll my own chart:

The chart above combines data from the 2009 spreadsheet from the US Census (all races) on the percentage of women by age bracket who were married, with the data on divorces by age in 2009 from Table 2 in this recent census paper.* Notice that while US divorce rates are significantly higher than UK divorce rates across the board, the same basic pattern we saw in the UK data exists in the US data minus the unexpected behavior for younger age brackets.

Taken together, this data soundly disproves the apex fallacy regarding divorce. The common belief that divorce rates are driven by men discarding older wives for a younger model simply doesn’t fit with the data. This is reinforced when you consider that the AARP found that 66% of the divorces in middle age were initiated by women (figure 2 on page 15). This fits with the historical trends of women of all ages initiating divorce, as shown in page 3 of this paper. Even in middle age women are still the ones driving divorce rates. The myth of the unloyal husband dumping his hapless wife once he feels it is to his advantage is generally just that (a myth). This won’t stop women from pointing over and over again to the rare case they know of in the media or in person where this has occurred, but in the scheme of things this is clearly an outlier. Across age ranges divorce is being driven by women, and the likelihood of a couple divorcing in any given year tracks very strongly with whether the wife feels it would be to her advantage not to keep her promise.

*The specific rates for each group in the US chart may not be exact. The figures in Table 2 from the new report on the total number of women in each age bracket vary slightly from the figures in the 2009 census report. This appears to be due to the nature of the sampling they did. Also, table 2 shows slightly different numbers of women and men divorcing and marrying in the same year. This would be expected when looking at different age brackets, but not the overall figures. At any rate, the differences aren’t large so the data still appears to be generally valid. Lastly, using the figures in Table 2 I calculated the overall rate of divorce per 1,000 married women in the US in 2009 at 19. This other source calculates it at 16.4 for the same year, however that report omits data from California, Georgia, Hawaii, Indiana, Louisiana, and Minnesota.